1. Field of Invention
This invention relates to gravity-driven car racing, specifically an improved cycloid-shaped ramp for race tracks such as used in the popular Pinewood Derby race.
2. Prior Art
Millions of Pinewood Derby races have been run since the inception of the race in 1953, mostly by Cub Scouts and their parents. But the currently available race tracks have a problem in the way the ramps are shaped. Refer to the prior art FIGS. 1 and 2 which point out side views typical of ramps currently in use. In one commonly used ramp in FIG. 1, the ramp material used to form either one lane or several of side-by-side lanes has unsupported regions, allowing the ramp to sag slightly under its own weight with an unspecified curvature. In this type ramp, the free sag also allows the curvature to vary depending on a car's weight, thus the car which is the leader can slightly increase the descent angle of its nearby competitors. In another commonly used ramp, as in FIG. 2, the ramp shape is predominately that of a straight plane inclined at a fixed angle. In such a ramp, as the horizontal is approached, a rather sharp curve in the ramp is used to allow the cars to transition into the horizontal coasting section of the track which can be up to 32 ft. (9.8 meters) long. However, the rather sharp transition curve can also cause excessive car weight from centripetal force.
To explain prior art in more detail, we refer now to the published information on 4 ramps as shown in the Information Disclosure section of this application. These ramps are:    1) Cub Scout Leader “How-To-Book”, Irving, Tex., 1987, p 9-40    2) Micro Wizard, of pinewoodderbytrack.com    3) The BestTrack™ of www.besttrack.com    4) The Derby Magic track of www.derbymagic.com
Referring again to FIG. 1, which shows a ramp 19, with a pinewood derby car 20 at the top, with the ramp end transitioning to a horizontal coasting run in the area of 21. All 4 ramps listed above have a main stand 22, which supports the ramp highest point, and also a secondary support stand 23. A brace 24, or 25 in FIG. 2, which keeps the main stand in a vertical position, is common in all ramps. The original wooden ramp design as in 1) above has a profile very similar to FIG. 1, where the recommended ½ inch thick plywood ramp has only a modest sag. The Micro Wizard ramp 2) is extruded aluminum and also has a support structure similar to FIG. 1. This ramp also has a sag similar to FIG. 1. The type of curvature shown by 1) and 2) is more at the bottom of the ramp than at the ramp top. Thus, when a race car pulls out of its descent at high speeds towards the bottom of these ramps, the centripetal force can be larger than necessary and cause the car weight to increase over 30%.
Referring now to FIG. 2, we see a straight inclined plane ramp profile with a sharp curve where the incline transitions to the level horizontal coasting section of the track. An example is the BestTrack ramp 3), of ordinary aluminum construction, with a brace 25 whose only purpose is to keep the main stand vertical. The transition to horizontal, shown in FIG. 3, of the BestTrack ramp, is a stiff pre-formed aluminum section 26 with a radius of curvature of 4 feet (1.22 meters). The Derby Magic ramp 4) also has a profile similar to FIGS. 2 and 3. This ramp is made from plastic, and prevents ramp sag before the transition curve by using a flat support structure of aluminum members for most of the downward ramp travel. But the centripetal force on the rather sharp transition section curves of ramp 3) or ramp 4) can cause the race car weight to be 3 times higher than on the straight sections of the ramp and coasting run. Thus an ordinary 5 ounce (0.142 Kg) race car will momentarily weigh almost 1 pound (0.45 Kg) and the centripetal force alone will be 8 times more than necessary. It has been observed that cars with uneven wheel-axle lubrication can begin oscillations back and forth when such a sudden weight increase occurs, such oscillations causing a substantial loss in the car speed. Also, cars with thin “speed” axles can suffer axle bending under the weight increase caused by excessive centripetal force.